Underground Pumped Hydro Storage is considered as power storage asset in Zeeland. Using Linny-R, a cost-driven model is made representing the power flows in the high-voltage grid of Zeeland. This model includes power production by nuclear power, fossil power generators, solar PV and windturbines, power demand from industrial companies, agriculture, mobility and dwellings, and the current market functioning using the day-ahead price and marginal costs. Modelling various scenarios, the impact of UPHS on the high-voltage grid is analysed, and discussed in a broader perspective of societal added value.